Suppose you want to known the length of the object shown below to the nearest tenth of a mm.
Using a ruler it is easy to measure the length of the object to the nearest cm,
or the nearest mm
but is it really possible to measure the length to the nearest tenth of a mm?
The divisions on the last ruler are so close that the human eye has difficulty distinguishing them. It is also difficult to manufacture rulers with such narrow divisions.
Vernier scales are a solution to this problem. Consider the diagram below.
The measurement of the object can be split into two stages. First measure the object using a ruler giving a distance of 3.4cm. Next use something else to measure how far the edge of the object is beyond the 3.4cm mark. The additional distance is 0.02cm so the length of the object must be 3.4cm + 0.02cm = 3.42cm .
The next page explains how a vernier scale can be used to find the additional distance.
Go to Why use vernier scales? How vernier scales work. Worked examples. Vernier Calipers.
Go up to Online Exercises.